Refrigerators and freezers in residential homes consume a large amount of energy, typically 13% of total energy consumption. It is the third largest user of energy in a residential building following space heating/cooling and water heating. Typically, a kitchen refrigerator consumes 500 to 700 kWh annually. In some regions in the United States, for example, New York, the average cost of electricity is $0.22 per kWh. The annual cost of electricity is $110 to $154. As the price for solar cells is dropped to $1 per watt, the use of solar-powered refrigerators is becoming economically advantageous.
On the other hand, the power grid is not always reliable. A severe thunderstorm, a blizzard, an average-intensity hurricane, or a breakdown of any part of a power grid will interrupt the supply of electricity. Once this occurs, the foodstuff in refrigerators starts to deteriorate. Therefore, refrigerators based on solar energy, if realized, should have a higher reliability. In regions without power grid, for example, remote areas in many countries, especially in developing countries, solar-powered refrigerators are the best option.
Refrigerators powered by solar photovoltaic cells have been used in regions without grid electricity, for example, to preserve immunizations in Africa. A central problem of solar-powered refrigerators is that solar energy is not continuous day and night. Refrigerators designed with very tight insulation, with backup batteries, or with variable-speed compressors to accommodate weak power sources have been proposed. However, those designs still have a huge fluctuation of cooling power due to the diurnal variation of solar energy because of the lack of energy storage capabilities.